1. Field of the Invention
The invention relates generally to devices and methods for obtaining cores from a sea bed.
2. Description of the Related Art
Current practices for seabed coring employ a coring device that is deployed from a surface vessel in a single coring run. The coring device relies on gravity to accelerate the coring device toward the sea floor and to provide the force with which the coring device penetrates the sea floor sediment. Alternatively, a drilling rig is deployed, either on a surface vessel or mounted on a remotely operated vehicle (ROV) which is landed on the sea bed. The drilling rig cores the sediment by rotary coring or by pushing a core barrel into the sea floor using the mass of the drill rig or drill string as a reaction mass against which to push the coring barrel. The core barrels are then recovered by wireline of with the ROV.
Among the disadvantages of existing systems and current practice is the limited penetration of gravity assisted drop corers, limited size (diameter and length) of cores due to restricted retrieval winch capacity and lack of attitude control for a drop corer. The drill rig method of taking cores is more precise and allows for greater penetration. However, these devices require dynamically positioned (DP) surface vessels for support. DP vessels are expensive and in limited supply. In addition, the drilling rigs themselves are costly to operate and maintain.
The present invention is directed to overcoming the problems of the prior art.